"goods costing a penny, as much as can be bought for a penny," Middle English peni-worth, from Old English peningwurð; see penny + worth (adj.). Figurative of "small amount" from mid-14c. Also generally, "value for the money given" (mid-14c.).
penny
penny-ante
pennyfarthing
pennyroyal
pennyweight
pennyworth
penology
pen-pal
Pensacola
pension
pensioner